Only moderate increase of cannabis potency in Europe in the last 10 years

In Europe, the THC contents of imported cannabis are typically between 2 and 8 per cent. However, the THC contents of cannabis grown indoor has increased due to the sinsemilla technique, where the fertilisation of the female plants is prevented. Only a small percentage of cannabis available in the United Kingdom, Germany, Ireland and Portugal is sinsemilla cannabis. Only in the Netherlands sinsemilla dominates the market with THC concentrations above 12 per cent. Authors note that "even here, local observers have argued that there is no evidence so far to suggest that this had led to an increase in observed problems."

They point out that "public health consequences of alcohol consumption are not a simple function of the strength of the beverage consumed, be it beer, wine or spirits. Rather, at population level, research suggests that it is the total quantity of alcohol consumed that is important rather than the concentrations in which it is sold." It is unknown how far this parallel holds for cannabis. Authors regard age of onset of use and frequency of use likely to be more influential than changes in potency in determining consumption levels. "In conclusion, we should not be unduly alarmed by the modest changes that have occurred in average cannabis potency; but neither should we be complacent, particularly as the evidence base is relatively weak and the relationship between potency, dose and problems remains poorly understood."

Source: www.cannabis-med.org

(King LA, Carpentier C, Griffiths P. Cannabis potency in Europe. Addiction 2005;100 (7):884-6)